1. Field of the Invention
The present invention relates to a liquid coating system for applying a liquid to an object of processing, and more particularly, to a belt-shaped nozzle for uniformly applying a developer or other processing liquid to a semiconductor wafer.
2. Description of the Related Art
In a developing process, among other manufacturing processes for a semiconductor device, a developer should be uniformly applied to a resist film on a semiconductor wafer within a predetermined time. The reason is that the developing uniformity for the resist film is generally supposed to depend on the state of development, so that the development is subject to irregularity unless the developer is first uniformly supplied to the whole surface of the wafer. Conventionally, therefore, liquid coating nozzles of various types have been proposed.
Disclosed in Published Unexamined Japanese Patent Application No. 57-52132 is a nozzle which has a plurality of discharge ports arranged so as to supply a developer like a shower. If the developer is supplied like a shower from the nozzle, however, many bubbles are produced on a semiconductor wafer, and the developing time is short by several seconds during which the bubbles exist.
Disclosed in Published Unexamined Japanese Patent Application No. 57-192955 is a nozzle which has a slit-shaped discharge port arranged so as to supply a developer like a curtain. In this nozzle, however, the pressure inside a liquid reservoir cannot be uniform, so that the quantity of discharge of the developer from that slit portion which is situated near a liquid inlet for supplying the developer is larger than that from any other portion. As a result, strings of liquid discharged from the nozzle are differed, the developing uniformity is lowered. Accordingly, the pressure for liquid supply must be increased to make the liquid discharge uniform throughout the length of the belt-shaped nozzle.
If the pressure of liquid supply to the nozzle is further increased, however, the impulsive force of the liquid becomes so great that the wafer surface portion first hit by the jetted liquid is overdeveloped, that is, the development is subject to irregularity.
If the liquid supply pressure is increased, moreover, the solubility of gas in the developer increases, so that bubbles are liable to be produced in the liquid discharged from the nozzle. As a result, those portions of the wafer surface on which bubbles exist are underdeveloped, so that the developing uniformity lowers.
If the liquid discharge is increased, furthermore, the quantity of waste liquid increases, so that the running cost swells.